1. Field of the Invention
The present invention relates in general to a tool for loosening or tightening a spark plug on a cylinder head of an internal combustion engine and more particularly to an improved socket wrench for a spark plug.
2. Description of the Prior Art
A socket for an impact wrench is well known in the art and used for loosening or tightening a spark plug. This socket is in the form of a hollow cylinder having a hexagonal opening adapted for fitting a hexagonal portion of a spark plug.
In some instances, a ring-shaped pressure sensor is installed between a spark plug and a cylinder head. This pressure sensor is used for measuring the pressure within an engine cylinder and thereby detecting a combustion condition of an engine. The pressure sensor is fixed to the cylinder head when the spark plug is tightened and is operable to convert a cylinder pressure to an electric signal by means of a built-in piezoelectric ceramic element, which electrical signal is taken out to the outside through a lead wire of the pressure sensor.
Since the automobile engine compartment is jammed with a number of engine accessories or automotive parts, a lead wire that is too long may possibly interfere with other parts or may possibly contact the same to be damaged or broken. For this reason, the lead wires of each part are usually designed to be of a minimum possible length. The pressure sensor is no exception to this. Accordingly, unless the pressure sensor is arranged to point in a predetermined direction, the lead wire may be too short to reach a part to be connected. For this reason, the pressure sensor needs to be arranged in a position of pointing in a predetermined direction.
Further, rotation of the pressure sensor may possibly cause a twist of the lead wire and a breakage of the same or the joint between the pressure sensor body and the lead wire may be pressed against the wire receiving groove to cause a crack at the joint.
However, with the conventional wrench socket for a spark plug, the pressure sensor remains rotatable until the spark plug is tightened and is thus driven to rotate in response to the tightening of the spark plug. Accordingly, it has been difficult to fix the pressure sensor while holding it in a position of pointing in a predetermined direction.